1. Field of the Invention
The present application relates to a method of producing an amide product mixture having a low content of secondary amines. The amide product mixture obtained contains a minor amount of tertiary amines and exhibits advantageous properties when used for the formulation of cosmetic products, such as shampoos and creams; foam cleaning compositions, e.g., for textiles and cars; and functional fluids, such as lubricants, metal working fluids and hydraulic fluids.
2. Description of the Related Art
The use of amides manufactured by amidation of monocarboxylic acids or their alkylesters, such as methyl esters, with secondary amines, such as diethanolamine, in a variety of cosmetic products, foam cleaning compositions and industrial fluids, is well known. In order to avoid the formation of undesired by-products, such as monoesters, diesters, and different types of esteramides, the amidation reaction has normally been carried out in a surplus of the secondary amine, such as diethanolamine, which, after the reaction, is present unreacted in the reaction mixture. The content of the secondary amine in the reaction mixture may vary within wide limits, but will be above 1% by weight. Where the reactants are a monocarboxylic acid and diethanolamine, the content of secondary amine is normally between 10% and 30% by weight and with the metylester of a monocarboxylic acid and diethanolamine as reactants, the content of secondary amine will be about 5-10% by weight.
The fact that the amide product mixture contains a large amount of secondary amine, such as diethanolamine, has not been considered as any real drawback as the secondary amine has contributed to improved anticorrosion properties when used in functional fluids and to a desired alkalinity and foam stabilization when used in cosmetic products and foam cleaning compositions.
Recently, more attention has been paid to the fact that secondary amines, such as diethanolamine, are toxic and form nitrosamines, which are carcinogenic in animal tests. Therefore, a reduction of the content of secondary amines is desirable. The content should, according to recommendations, be less than 1% by weight.
Thus, one object of the present invention is to produce an amide product mixture which contains secondary amines containing less than 1% by weight.
Another object of the invention is that the method of producing the amide product mixture shall be simple to perform and that the amide product mixture shall be useable without any additional cleaning and/or working-up processes.
Another object of the invention is to keep the formation of esters, diesters and esteramides to a low level.
Still another object of the invention is that the amide product mixture shall at least have about the same corrosion inhibiting ability and/or defoaming properties in functional fluids and at least about the same foam stabilizing properties in cosmetics and foam cleaning products as the corresponding amide product mixture with high contents of secondary amines.